While the use of distinct and separately wound stator segments provides some benefits, it potentially increases the complexity and costs of manufacturing operations. For example, in many segmented stators the stator segments are wound individually and one or more manufacturing steps are required to appropriately interconnect all the individual stator coils to form the phase windings. In such conventional stator assemblies, because the distinct and separately wound stator segments are not coupled together during the winding operation, some retention structure is required to hold the stator segments together when they are formed into an annular stator. The requirements for the coil interconnecting step, the materials and equipment required for the same, and the need for a secondary retention mechanism often require a significant capital investment in manufacturing equipment to manufacture such machines and significant material cost adds to the component costs of machines made according to such processes.
In an effort to overcome some of the limitations associated with stator assemblies having separately-wound stator segments as described above, approaches were developed wherein magnetically-interconnected stator segments were physically coupled to one another prior to the winding operation such that the coils could be formed in an interconnected manner. In known conventional approaches, the stator segments were interconnected though the use of hinges, sometimes referred to as puzzle lock connections, or through the use of thin interconnecting bridges of magnetically permeable materials. Such interconnecting structure often requires relatively complex stator lamination constructions, which can increase the overall manufacturing costs for a machine utilizing such a design. Moreover, the manufacturing steps required to couple the distinct stator segments together via the hinge or puzzle lock structure increases the cost and complexity of the manufacturing process.
One limitation of stator assemblies using interconnecting puzzle pieces or bridges is that the stator assembly is often fairly inflexible and access to the stator teeth during the winding operation is somewhat limited. These limitations can restrict the extent to which magnetic wires can be placed in the stator to form the stator windings or, in other words, the “slot fill.”
An alternate conventional approach for forming a “segmented stator like” machine that does not require the use of hinges or puzzle locks relies upon the use of a stator assembly formed from groupings of stator segments that are magnetically coupled together by a thin, interconnecting bridge. Such a design is disclosed, for example, in Japanese Patent B-30107085. Through the use of such a bridge, it appears possible to have a grouping of three stator teeth that are coupled together magnetically by a bridge element but that are opened to some degree allowing greater access to the stator teeth and, thus, greater slot fill. One limitation of this approach is that the stator assembly will typically require more than three stator teeth such that construction of the complete stator assembly will require the use of multiple groupings of three stator segments, which necessitates multiple manufacturing steps of coupling the winding coils from the stator groupings together and structure for coupling the multiple stator groupings to form an annular stator. Such additional manufacturing steps and structure can significantly increase the costs and manufacturing complexity associated with such stators.
The present disclosure describes several embodiments of a stator assembly that are designed to address the described and other limiting characteristics of conventional segmented stator assemblies.